1) Its allowed me to be more accepting of myself and others for the odd little quirks that we exhibit. As a result, I've calmed down more when I deal with other people, since I could put a clearer reasoning for why people think differently than me. This also goes hand in hand with just naturally maturing, but I feel that reading about personality helped expedite the process.
2) I think the biggest challenge is understanding the fluidity of the traits that the types represent. What typically determines someone type is the prevalence of traits when viewed against other people and the traits they exhibit. Its culturally derived, in other words, so there really is no clear base line for behavior.